Cryptosporidium is a protozoan parasite found in contaminated water. It has been increasingly recognized as the cause of outbreaks of diarrhea when water supplies become contaminated. In normal individuals, it is a self-limited disease. Among immunocompromised individuals with AIDS, cryptosporidium can cause severe diarrheal disease, gallbladder disease (cholecystitis), and inflammation of the pancreas (pancreatitis).